The (Surprising) Truth About Salt

How Low Can We Go?

Last April, after extensive talks with food manufacturers, Dr. Angell and the DOHMH published voluntary limits on sodium in 62 categories of packaged food (breakfast cereal, canned soup, and more) and 25 categories of restaurant food (hamburgers, fries, muffins) to lower sodium throughout the food supply. Sixteen food companies and restaurant chains, including Heinz, Unilever, Kraft, and Subway, have already signed on. The goal: a 25 percent reduction over the next five years, which is in line with the American Medical Association's call for a total of 50 percent over the next 10.

Dr. Angell calculates that this should get us closer to 2,300 mg, the maximum amount of sodium recommended in the current Dietary Guidelines for Americans, 2005, the government's official road map for building healthy American diets; it covers everything from school lunches to dietitians' advice to their clients. But the new 2010 guidelines, anticipated for release at the end of the year, dump this old number for an even lower one: 1,500 mg  about two-thirds of a teaspoon of salt a day. That amount is the so-called "adequate intake"  the minimum our bodies need to function and to maintain good health.

Why drop so low? The number one reason, says Lawrence Appel, M.D., M.P.H., professor of medicine at Johns Hopkins University and member of the 2010 U.S. Dietary Guidelines scientific advisory committee that recommended the new sodium level, is the direct relationship between sodium and blood pressure: The less you take in, the lower your blood pressure. (Other researchers have a problem with this, saying it's not that simple.) In the 2001 DASH (Dietary Approaches to Stop Hypertension-Sodium) trial, which tested the effects of a healthy, monthlong, low-sodium diet in people with high and borderline-high blood pressure, subjects' blood pressure dropped considerably when they consumed about 1,500 mg of sodium a day. In addition, "you're dealing with a chronic problem that develops over time," he says. "The idea of somebody just waiting until they have hypertension and then flipping into a low-sodium diet is somewhat like saying, well, let's just wait until you get your first heart attack and then we'll start telling you about saturated fat."

But drastically cutting sodium to 1,500 mg a day astounds some physicians. "The goal is completely unrealistic. This is far too low," says Neils Graudal, M.D., a Danish researcher who has published several large, influential research reviews showing that cutting sodium affects a lot more than just blood pressure. "There's no evidence that directly links low sodium intake to better survival," he adds. Furthermore, he thinks it's unrealistic to expect anyone to actually adhere to the new guideline, considering that one store-bought corn muffin (590 mg) and a cup of chicken noodle soup (840 mg) come in just under the limit. A dinner out can cost you a couple of days' worth of sodium: At Chili's, an Asian Salad with Grilled Chicken has 2,700 mg, and a Cajun Pasta with Grilled Shrimp, 3,200. Prepared salad dressings can have 505 mg per serving; ketchup, 167 mg per tablespoon; pasta sauce, 1,054 mg per cup. Even with the Initiative's reductions, it will be hard to find things to eat.

What's more, doctors and public health experts have long assumed that if we all just knew how to lower the salt and we were in a food environment conducive to eating less of it, we'd cut back. But the findings of a recent study on sodium appetite  how much our bodies naturally "want"  contradict that assumption. When researchers at the University of California, Davis, and Washington University in St. Louis looked at the sodium intakes of 19,151 people in 33 countries with vastly different cuisines, they found the amount people typically consumed fell within a narrow range (2,691  4,876 mg/day; the average was 3,726 mg/day); even when scientists tried to get people to lower their sodium to 2,300 mg, the subjects couldn't do it, and they ended up at about 2,800 mg/day. The researchers hypothesize that we might have evolved an appetite for the mineral along with a physiological set point that ensures our body's need for sodium in multiple systems is satisfied.

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